THURSDAY, Feb. 4, 2016 (HealthDay News) -- Sleeping too few or too many hours a night may lead to excessive weight gain during pregnancy, a new study suggests.

"We know that poor sleep in pregnancy has been linked to adverse pregnancy outcomes," wrote researcher Dr. Francesca Facco, who's with the U.S. National Institute of Child Health and Human Development.

"Our findings provide a potential mechanism [weight gain] for poor sleep in pregnancy and adverse outcomes," she said in a news release from the Society for Maternal-Fetal Medicine.

Previous research has suggested that poor sleep is associated with weight gain and obesity in women who are not pregnant. The authors of this new study wanted to examine a possible link between sleep and weight gain during pregnancy.

The study included 751 pregnant women whose sleep was monitored for seven straight days. About two-thirds of the women slept between seven and nine hours a night.

The researchers found that short or long sleep duration was associated with extra weight gain during pregnancy.

The study is to be presented Thursday at the Society for Maternal-Fetal Medicine's annual meeting, in Atlanta.

Research presented at meetings is considered preliminary until published in a peer-reviewed medical journal.